The roster of speakers tells the story: From movement-conservative keynote speaker Ted Cruz, the outspoken new Republican senator from Texas, to libertarian Sen. Rand Paul (R) of Kentucky and Sen. Marco Rubio (R) of Florida, an establishment favorite, different strains of conservative thought will be on full display.

Other speakers will shift the focus to the recent, uncomfortable past. Mitt Romney, not a beloved figure in conservative circles, will make his first public address since losing to Mr. Obama last fall. And Sarah Palin, the GOP’s vice presidential nominee in 2008, will return to the spotlight after her recent split with Fox News.